2012: fix mix-up of semantic/syntactic

Fixes golang/go#21065

Change-Id: I73683ee8cd20eab4808b5130f848fa7fe2103c98
Reviewed-on: https://go-review.googlesource.com/49570
Reviewed-by: Kevin Burke <kev@inburke.com>
diff --git a/2012/splash.article b/2012/splash.article
index 39b9104..fd2cda2 100644
--- a/2012/splash.article
+++ b/2012/splash.article
@@ -1061,7 +1061,7 @@
 
 A key point about this transformation is that, because the input and
 output are both in the canonical format, the only changes made to
-the source code are semantic ones.
+the source code are syntactic ones.
 
 A similar but more intricate process allowed `gofmt` to be used to
 update the tree when the language no longer required semicolons